Rainwater collection systems are usually considered to be a
rural technology. The discussions of cost versus benefit and of feasibility
commonly centre on the individual household. However, for studies carried out
by and for governmental water agencies, the target area is more likely to be a
town or a city. More: broadly based estimation techniques for estimating
rainwater collection system viability are required in this case.

This paper will show that rainwater collection may
contribute to urban water supplies and will provide an outline of some of the
calculations that can be done to estimate that contribution based on
consideration of the city as a whole.